Pro-Series SK10 Lyndex Style CAT40 Collet Chuck with 120mm Gage Depth ~ Collet range is 0.069-0.393″. ~ Runout is less than or equal to5 Micron. ~ Dual contacts of taper and flange. ~ Increases spindle contact by 53% over standard holders. ~ Prevents tools from pulling into spindle. ~ Balanced to 20,000 RPM.